Using javascript fetch and invoking a rest service that returns a blob if successful, otherwise returns an error message as json. How would this be handled in the fetch? The actual service is a asp.net web api implementation that returns a FileStreamResult (or FileContentResult) when successful, otherwise returns an error code with json containing the error message. Below is an example of what I'm trying to do:

fetch('flowers.jpg').then(function(response) {

  if(response.ok) {

    return response.blob();

  } else {

    return response.json();

}



}).then(function(myBlob) {  // here I would also like to function(jsonError)

  var objectURL = URL.createObjectURL(myBlob); 

  myImage.src = objectURL; 

}).catch(function(error) {

  console.log('There has been a problem with your fetch operation: ', error.message);

});